Stoker damper control



' April 3, '194 5. Fl'w. STUART v 2,372,853 sTbKER DAMPER- CONTROL.-

FiledrAug. 9, 1939' 2 Sheets-Sheet l .BY I

W ATTORNEY.

April 1945-. F. w. STUART 2,372,863

STOKER DAMPERCONTROL v v filed Aug. 9, 1939 2 Sheets-Sheet 2 INVENTOR.

.E-CEELDZLSTLTETT Patented Apr. 3, 1945 s'roxsn DAMPER con'rnoL Fred w. Stuart, Cincinnati, Ohio, asslgnor to Perfex Corporation, Milwaukee, Wis., a corporation of Wisconsin Application August 9, 1939, Serial No. 289,157

29 Claims.

. The present invention-relates in general to automatic air damper controls for furnace stokers and the principal object of the invention is to design an improved air damper control for re ulating the amount of combustion air delivered to the furnace retort.

In the usual type of stoker equipped furnace it is customary to provide a constant speed fan for delivering forced combustion air to the retort of the furnace and which operates each timethe stoker motoris automatically actuated to feed fuel to the retort. During the intervals that the stoker is not operating suflicient air for natural draft is provided to maintain the fire. In the initial operation of the fan the blast of air through the comparatively low fire bed blows "fly ash" through the'furnace which is extremely objectionable and renders the furnace less efiicient in operation by depositing the ash throughout the furnace structure and pipes. This fly ash likewise pollutes the air and is objectionable from a health standpoint.

It is an object of this invention to eliminate the fly ash disadvantage by providing a retard air damper valve or shutter for restricting the -amount of air delivery from a stoker fan to the forced air into the low fire bed of the retort at damper in which a delayed opening of the damper takes place upon initial stoker operation under control of a room thermostat while during holdfire periods when an interval timer takes control to maintain the'fire, the opening of the damper does not take place.

Other objects and advantages reside in certain novel features of construction, operation, arrangement andcombination of the parts which I will be hereinafter more fully described and parfire bed during the initial operation of the stoker v and which gradually opens and permits maximum air volume after the stoker has been operating for a while.

A further object is to provide a, simple and ef ficient control means for controlling the operation of a stoker air damper, whereby the damper is gradually brought to its full open position and positively maintained in its op p n during continued stoker operation.

A further object is to provide a static air pressure responsive means whereby the damper control means is prevented from actuating the damper until the fuel. bed in the retort has been built up to proper thickness for eillcient firing.

An additional object of the invention is to provide a simple, economical and easily installed air damper device which greatly increases the eiii ciency of stokers and at the same time minimizes the production of fly ash dimculties.

- A further. object is to design an improved heat motor type control for actuating the stoker damper in th manner aforesaid.

An interval timer is usually provided to maintain the fire alive during periods in which the room thermostat is not calling for heat. Upon the operation of the interval timer during such hold-fire" periods the fire bed is usually at avery low stage and to pass the full volume of ticuiarly pointed out in the appended claims.

This invention is in the nature of an improvement upon my prior Patent No. 2,122,050 issued June 28, 1938.

The invention is illustrated in its preferred form in the accompanying two sheets of drawings in which:

Fig. 1 illustrates the application of the control device upon a stoker installation;

' Fig. 2 is across sectional side elevation of the control mechanism;

Fig. 3 is a left end view of Fig. 2 taken alonz the line 3-3 of Fig. 2;

Fig. 4 is a similar view as Fig. 2 showing the control device in its fully operated position;

Fig. 5 is another view of the control device in an intermediate operated position;

Fig. 6 is a chart indicating the operating characteristics of the control device; while Fig. 'l is a schematic wiring diagram of the stoker control system. I

The control device indicated generally at III is preferably supported upon the air conduit or duct ll of a conventional stoker unit between the retort l2 and theair fan I311. The stoker coal hopper is indicated at M and also preferably encloses the fan Ila and the operating portion of the stoker screw fuel feeding mechanism. The

fuel feeding mechanism or conveyor such as a feed screw may be arranged along the side of furnace or boiler not shown.

The control device includes a metal casting 1 l5 for supporting the various control elements thereon. The supporting casting I6 is secured over an opening'in the air duct H by means of a number of bolts IS. A sheet metal casing I1 01 generally rectangular shape rests on top of supporting casting l5 and is completely lined on its inside surface as shown with suitable thermal insulating material such as asbestos. A metal cover plate l8 rests on-top of the casing H for closing the top thereof. Formed integral with the cover plate I6 and projecting downward therefrom is a cylindrical bellows partition l9 which is also arranged to project slightly into a circular baflle wall 20 projecting upward a short distance from the bottom of the supporting casting I5. The bellows partition I9 forms a bellows compartment 2| within which there is arranged an expansible and contractable bellows or heat responsive element 22 which is suitably filled with a volatile gas or liquid which has the propertyof expanding when subjected to the action of heat. The upper end of the bellows 22 is provided with a threaded stud whereby the bellows may be suitably supported from a boss 23 formed in the cover plate I8.

Arranged adjacent to the bellows 22 and in thermal relation thereto is an electrical heat producing heater 24. This heater may' be of any conventional form and comprises a resistance wire wound around an insulated base member as shown. Heater 24 is supported by a bracket member 25 fastened to the top of cover plate l8 by screws as seen in Fig. 3. The supporting end of heater 24 may be made of porcelain and carries a pair of terminal screws for the attachment of the connecting terminal wires for the heater. The combination of the electric heater 24 and the bellows 22 responsive thereto, constitutes a heat motor whose function is to perform certain work as will be pointed out.-

An electromagnetic means such as a solenoid 26 is also'arranged on top of supporting casting l5 and is preferably supported as shown by means of a pair of screws threaded into the sides of the casing l1. The solenoid 26 is provided with an operating armature 21 which is adapted to move upwardwhen the solenoid 26 is energized.

The bottom side of the supporting casting I5 is arranged to form an air chamber '26 immediately above the opening in the air duct A sheet metal protective cover 26 for the control device'is provided having a series of louvres 30 -asseen in Fig. 3 to permit the hot air to escape,

as will be pointed out. The cover 29 is supported in the side of easing H. A counter balance weight 38 is carried on the short end of lever 36 while a mercury switch device 39 is supported upon the other end of the switching lever 36 beyond its connection with the rod 35. An air adjustment means 40 for regulating the response of the disc 34 is adjustably arranged on top of the supporting casting l5 around the rod 35.

Arranged within the air chamber 28 and below the supporting casting I5 is an operating lever or arm"4| pivoted by a pin 42 to the sides of cast- 3 ing l5. One end of the operating lever 4| is arranged to carry in a suitable manner, as shown, a mercury switch 43 having two sets of contacts arranged therein; one set, 44, controlling the operation of the solenoid 26, while the other con- .tact set, 45, is adapted to control the circuit to the heater element 24. A short link member 46 connects the contact end of operating lever 4| with the armature 21 of the solenoid 26. A second link member 41 connects the same end of operating lever 4| with a detail damper valve or shutter 48 which in turn is pivoted by a pin 49 to the side of casting l5 as shown. The damper Ail-normally and substantially obstructs the air duct II as shown in Figs. 2 and 3.

The lower end of operating bellows 22 is provided with an operating pin 50 adapted to engage.

the top side of a push lever 5| which in turn normally is in engagement with the short end of operating lever 4|. An extension arm 52 is suitably fastened by screws, as shown, to the short end of operating lever 4|.

Arranged within the air chamber 28 and formed integral with the supporting casting I5 is an air passage 53 having its lower end projecting into the top of the air duct The bottom end of air passage 53 is provided with a scuttle or defiector 54 for closing the end thereof and is pivoted to the end of passage 53 by a pivot pin 55. A counter balance weight 56 is connected to the deflector 54 for normally maintaining the opening in passage 53 closed. A pin 51 adapted to be engaged by the end of extension lever 52 is arranged upon an up-turned portion of the defiector 54 so that when the lever 52 is operated the deflector 54 is opened.

An air adjusting plate or disc 56 for regulating the amount of air passing from the bellows chamby means of a number of sleeves 3| and bolts 32.

secured to the supporting casting I5 and the cover I. These bolts 32 'also hold the cover l8 and the casing II in place onto the casting l5.

Formed integral with the supporting casting I6 is a static pressure cylinder casing 33. A pres-' sure responsive means such as plunger or static pressure disc 34 is arranged for reciprocal movement within the cylinder 33 (See Fig. 3). The

ber 2|, is adjustably positioned by screw 56 on the top of cover plate l8 and immediately above the bellows chamber 2|. A series of air openings 60 are formed'in casting l5 below the heater 24 for a purpose to be described. A second air adlusting plate (see Fig. 3) is arranged above the electrical heater 24 and comprises a flat plate 6| adjustably supported by screws 62 upon support- .ing bracket 25. Several openings 63 in the plate 6| and in the supporting bracket 25 are arranged in coinciding relationship so that when the plate 6| is adjusted more or less air is permitted to pass through the openings 63. i

Referring to Fig. '7, a circuit arrangement for operatingthe control device is illustrated. This includes a pair of line conductors 64 and 65 connected to a source of operating current, a conventional type of room thermostat 66 connected in series, with line 64, and an interval timer 61 of any desired form connected in parallel with the room thermostat 66. The interval timer 61 may beclock driven and isarranged to close its I contacts preferably for two or three minutes each half hour or each hour, or any other desired adjustable period.- The purpose of this timer is to operate the stoker during hold-fire" perio s when the room thermostat 66 is not calling for heat, in order to maintain the fire. The motor I; for operating the fan i3a and stoker is connected across the line conductors for operation. Solenoid'winding 26 is connected in series with contacts 44 of mercury switch 43 and in series with the pressure switch contacts 39, across the line conductors, while the heater 24 is connected in series with the mercury contacts 45 and the static pressure switch contacts 39 across th line conductors.

In describing the operation of the control device, its normal inactive position is that assumed as shown in Fig. 2 in which the air damper 48 substantially obstructs the air duct II by assuming a vertical position. In this position sufllcient openings are provided around the air damper 48 to permit a small amount of air escapement to take place, for the purpose of providing a certain amount of natural draft to maintain fuel bed alive.

Assume now that th room thermostat 66 is operated to close its contacts upon a fall in room temperature. When this occurs the fan and stoker motor i3 is started into operation and the stoker screw begins to supply fuel to the fire bed.

' Assume also that the fire has been operating for some time under hold-fire conditions and consequently a considerable amount of burnt coal or ashes has accumulated in the retort. Under ordinary circumstances the starting of the stoker and the fan would immediately blow this fly ash through the furnace. This, however, is prevented by the invention in which a delayed time interval is provided before the full effect of the fan operation is permitted to exert itself upon the fuel bed. Under these conditions approximately per cent of the full volume of air passes around the sides of the damper 48.

With the stoker screw now feeding green coal upon the fire, static air pressure in the air duct Ii is gradually built up by the accumulating thickness of the fuel bed. This air pressure eventually builds up to a certain or predetermined static pressure value in the duct and in front of the air damper 48. The pressure responsive disc or piston 34 within the static pressure cylinder is thereby actuated responsive to the increasing static pressure, and moves in an upward direction forcing the connecting rod 35 upward so that the operating lever 36 is caused to move about its pivot 31 until a position is reached wherein the mercury switch 39 is tilted to close its contacts. The counterbalance 38 is provided for the purpose of balancing the weight of the mercury switch to render the device more sensitive.

The closing of the static pressure switch 39 establishes a circuit (see Fig. 7) forthe electric heater 24 extending in series with the normally closed contacts 45 of mercury switch 43, the now closed static switch contacts 39, and the line conductors 64 and 65. From the foregoing it is seen that theciosing of the circuit to the heater 24 is prevented until the static pressure in the air duct has been built up to a certain value, thereby indicating a certain thickness of the fuel bed on the retort. The resistance winding of the electric heater 24 being now energized, it gradually begins to emit heat. This heat emitted by heater 24 is arranged to effect the expansion of the bellows 22 by passing it by convection over the bellows.

ant heat is transferred thereto. In order to cir- 1 distance.

culate the heat in the most efiicient manner over the bellows, the series of openings is arranged to permit the entrance of a portion of the air from the air duct ii. This circulated air is passed around the heated element of heater 24 where it is heated and passed between the ends of baille plate 20 and the end of bellows partition l9 as indicated by the arrows in Fig. 2. This heated air further passes within the bellows chamber 2| around the bellows 22, heating the same and then passing upward through the adjustable openings'in the top of cover i8 and the adjusting plate 58. of the enclosing cover 29 through the louvres 30 in the sides thereof. The openings 63 in the top of heater 24 are adjusted to pass a portion of the heated air.

The expansible fluid in the bellows 22 is affected by the passage of heat over the bellows and accordingly tends to expand the bellows so that the operating pin 50 is caused to exert a downward thrust against the short lever 5|. This effort is transmitted by lever 5| to the short end of operating lever 4|, thereby causing it to be rotated in a counter-clockwise direction about pivot pin '42. Eventually, after a time interval, an intermediate position is reached in which the operating lever 4| assumes a horizontal position as shown in Fig. 5 wherein the mercury in switch 43 disengages itself from contacts 45. During this same movement the long end of the operating lever 4| forces the armature 2! through link 46 into the core of the solenoid 26 for a short Also the connecting link 41 moves the air damper 48 substantially to the intermediate position shown in Fig. 5. In this position of the air damper 48 a-greater amount of air is caused to pass through the air duct II from the fan l3a,v

and since the fuel bed on the retort l2 has been built up to some substantial thickness in the meantime, this increased air flow causes the fire to be expanded to a considerabl extent, thereby increasing combustion. It is seen that this increased combustion takes place only after fresh Since the partitions l3 and 20 sep- V arate the bellows from the heater, no direct radifuel has been fed upon the fire and when the possibility of blowing fly ash through the furnace has ceased to exist.

It will be appreciated that the time interval which it has taken the damper to assume the foregoing position may comprise a substantial period, of for example several minutes, due to th time required to build up pressure in the cylinder 33 and the lag in the time required to heat the element of heater 24 and for the bellows to respond. This timed period is suiiicient to prevent the blowing of fly ash through the furnace. When the operating clever 4| assumes the position shown in Fig. 5 with the contacts 45 disengaged, the circuit for the electric heater 24 extending therethrough is disconnected and the heat generated by heater 24 is terminated. Due to the lag in the cooling of this element, the bellows 22, however, may continue to expand a further slight amount. I

The mercury switch 43 is designed to open contacts 45 and immediately close contacts 44 and The air may further pass out permitting the full force or volume of air delivery I from the fan to pass through the air duct l l and afi'eet the fuel bed so as to greatly increase the size of the fire.

As a further result of the energization of solenoid 26', the end of extension lever 52 engages the deflector pin 51, forcing it downward and rotating the deflector 54 about its pin 55 so that the air passage 53 now is opened. The deflector 54, it is seen, projects a slight distance into the forced air stream passing through the air duct I I and serves to scoop up a portion of this air and divert it through the passage-53 and around the outside of the bellows 22, through the bellowschamber 2|, and out through the adjustable openings in the top of this chamber and the adjusting plate 58 where it is permitted to escape. This cool air tends to quickly restore the bellows 22 to its retracted position, within a shorter period than would be required for it to cool in the ordinary course as by convection. At this time cool air is also permitted to pass through the chamber 28 and the'holes 60, around the heating element 24 and out of the adjustable openings 68 to further assist in cooling off the heating element to more quickly restore the heater to a relatively Qcooled state.

The stoker is now operating to its fullest extent, feeding fuel to the hot fire while the fan is feeding forced combustion air at its fullest volume to the now open air duct I I. The control device will remain in the operated position shown in Fig. 4 as long as these conditions exist.

From the foregoing operations of the control device it will be seen that because of the relatively distant thermal relationship of the bellows to the heater in the starting operation due to the inter-position of the walls l9 and 20, it requires an appreciable time interval for the full action of the bellows to take effect upon the air damper- 48, while when the solenoid 26 has taken control,

the damper is immediately opened to. its fullest extent. The heater 24 and the bellow 22 are gradually cooled oil by the passage of the forced cooled air through the passage 53 and the open- I ings 60.

After the heat generated by thefurnace has reached the vicinity in which the thermostat 66 Y is located, the thermostat operates to open its contacts thereby disconnecting the solenoid 26 from its operating current source and at the same time stopping the operation of the stoker motor II. The stopping of the motor I8 stops the fan Ila from forcing air through the air duct ll thereby permitting the disc 34 in the static pressure chamber 33 to drop downward to its normal position shown in Fig. 2, and opening the mercury switch contacts 39. As a further resultthe armature 21 of solenoid 26 is released causing the air damper- 48 to pivotally drop downward and assume the position shown in Fig. 2 in which-it substantially obstructs the air. passage of the air duct ll. crating lever 4i and the weight of the air damper linked thereto, the extension lever 52 is moved in an upward direction disengaging itself from the deflector pin 51 and permittin the deflector 54 to close the end of the diverting air passage 53 by reason of the counter balance weight 55. During the time it may have taken for the room thermostat 66 to respond to th heat of the stoker operation, the bellows 22 has been cooled to its normal contracted state while the heater 24 has likewise been cooled oi as shown in Fig.2. The control device remains in the aforesaid dormant position until another call for heat takes place.

Under ordinary circumstances, after the room thermostat has actuated the stoker until it has become satisfied and remains so for a considerable time interval, the fire would become extinguished if it were not for the provision of the interval timer 61 which at periodictime intervals closes its contacts as has been pointed out to operate the stoker and maintain the fire alive. The action of this interval timer 61 upon the control device, however, is arranged so that the control device is not actuated to its fullest extent because of the short time, for example three minutes, in which the timer maintains its contacts closed and then opens them. If the. full volume of air were immediately forced into the comparatively small fire, it would burn too quickly and therefore may burn itself out before suflicient fuel were-fed into the retort by the motor II. This short time interval is not suflicient for the static switch 39 to operate to its fullest extent or if it should operate the heater 24, the heat, generated thereby would not be completely effective upon bellows 22 to operate it due to the relative lag in the response of these devices. Therefore the air damper 48 is not act'uated from its vertical position as shown in Fig. 2. The forced air from the operation of the fan is substantially prevented from passing into the stoker retort by the air damper but the stoker feeds fresh fuel upon the fire for the full three minutes of operation of the interval timer. After the operation of the interval timer the stoker is stopped and the natural draft of air passing around the sides of the air damper 48 in the duct ll maintains the fire bed active with the additional fuel fed to the fire.

It will be appreciated that by adjusting the openings by means of the adjustable plate 58 and the screw 59, the response of the bellows 22 may be regulated to any desired time interval by permitting more or less of the heated air from the bellowschamber 2| to'escape out of these openings. Similarly, by adjusting the adjustment plate 6|, any variable amount of air is permitted to escape from the heater chamber to assist in its cooling or to prevent'lts cooling too rapidly as desired. By thermally insulating the casing II the full 'eifect of the heat from heater 24 is not permitted to escape by convection or radiation through the casing walls I! and thereby assists in more readily regulating the response of the bellows 22. I

' Referring now particularly to Fig. 6, this drawing represents a chart showing the operating characteristics of the control device for two dif- Due to the relatively long end of opferent operating periods for example. The dotted line indicates the operation of a stoker in which the room thermostat is arranged to operate the stoker for periodic cycles of 10 minutes on" and 5 minutes off." This periodic cycle operation of the room thermostat, it will be appreciated, will vary with weather conditions. In mild weather the on period will be short and the of! period will be long, while in cold weather the reverse will be true. The full line indicates cyclic operations for a stoker which is run for 20 minutes and stopped for 10 minutes. The per cent of damper openings in the air duct is charted against the timed periods in minutes. It will be noted from this chart that the air damper is arranged to always permit 10 per cent air delivery through the air duct where the stoker is operating. The point 68 indicates the time required, in this case two minutes, after the stoker is started, for the static pressure to build up in the air duct, plus the time it takes for the heater 24 to heat up and the bellows 22 to begin to respond thereto. As the bellows gradually expands, the damper is gradually opened and after an additional interval of five minutes as indicated at 68 it is opened for 50 per cent of its full openings in the air duct. At this time the solenoid 26 takes control and immediately opens the air damper to its full 100 per cent opening as indicated at Ill. After a further run of the stoker for three minutes, during which the damper is open, the stoker is stopped by either the room thermostat or interval timer as the case may be, and the solenoid deenergized whereupon the air damper immediately drops from the point It to the point '12 which represents a damper opening of 30 per cent. The air damper is stopped in this position instead of the closed position indicated at 68 because of the residual heat remaining in the heater 2d and the lagging cooling response of the bellows 22, due to the comparatively short stoker operation (10 minutes) which does not allow the control device to be fully cooled and restored to its'normal position as shown in Fig, 2. This prevents the fire from being strangled by completely shutting off the air flow after this comparatively short run, there by preventing excess smoking. After an off period of five minutes, during which the residual heat in the bellows is being gradually dissipated, the point indicated at it is reached by the damper which represents an opening of slightly over 20 per cent.. At the point 73 the stoker is started again and the damper openings are progressively brought about as has been pointed out.-

The full line on the chart indicates, as has been stated, an on period of 20 minutes and an off period of 10 minutes for the stoker. Due to the longer time intervals between stoker operations, it will be seen that the control device is fully restored to its normal cooled position as seen in Fig. 2 and the air damper is restored to its full air 65 From the foregoing description it will be seen duct closin position after each operation.

that the control device comprises a simple and efiicient'arrangement whereby a delay is interposed between the feeding of fuel to a. fire and, the delivery of forced air to the fuel bed so that the objectional propagation of fly ash through more rapidly than would be the case were the bellows cooled simply by convection.

Should it occur that during an operation of the stoker with the air damper fully open, that a furnace is substantiallyeliminated. Moreover,

the passage of forced air to the fuel bed is predicated upon the thickness of the bed of fuelso that only when the bed is of the proper thickness for efilcient combustion is the forced air permitted to be passed to the fuel air volume is regulated upon the initial actuation of the stoker. This tends to maintain a uniform fuel bed. 7

In addition the air damper is arranged so that it is held locked in. its fully opened position as long as the stoker is operating. The arrangement of the deflecting 'air passage 53 enables the bellows to be retracted to its normal position bed, thereby the.

a blow-hole" manifest itself in the fuel bed, the forced air would immediately pass through this holef and rapidly burn the fire out. This is prevented however by the static pressure drop which would immediately occur in the air conduit and result in the static pressure switch restoring to normal thereby opening its switch 39. Switch 39 opens the circuit of the solenoid 26 and this closes the damper to shut off the air flow.

It will be appreciated that any number of modifications of the invention may be devised by those skilled in the art without departing to any great extent from the principles of the invention,

and it is therefore desired that the invention be not strictly limited to the exact form of the disclosure pointed out, but only to the extent of the appended claims.

What is claimed is: 1. In a control system for a stoker mechanism having fuel feeding means and air feeding means,

the combination of, means responsive to the demand for heat from the stoker mechanism for controlling the operation thereof, a controller for varying the feeding of air, a time delay mechanism actuated upon demand for change in operation of said stoker mechanism for shifting said controller to vary the air delivery after a period of time has elapsed, and holding means for normally preventing return of said controller to its initial position irrespective of said time delay mechanism.

2. In a control system for a stoker mechanism having fuel feeding means and air feeding means, the combination of, means responsive to the de mand for heat from the stoker mechanism for controlling the operation thereof, a controller for varying the feeding of air, a time delay mechanism actuated upon demand for change in operation of said stoker mechanism for shifting said controller to vary the air delivery after a period of time has elapsed, and means actuated upon said controller being shifted to a predetermined new position for preventing return thereof While causing said time delay mechanism to return to its initial position.

3. In a. control system for a stoker mechanism having fuel feeding means and air feeding means, the combination of, means responsive to the demand forheat from the stoker mechanism for controlling the operation thereof, a. controller for varying the feeding of air, a time delay mechanism actuated upon demand for change in operation of said stoker mechanism for shifting said controller to vary the air delivery after a periodof time has elapsed, means actuated upon said controller being shifted to a predetermined new position for preventing return thereof while causin said time delay mechanism to return to the combination of, means responsive to the vdemand for heat from the stoker mechanism for controlling the operation thereof, a controller for varying the feeding of air, power operated means energized upon demand for change in. operation of the stoker mechanism for actuating said controller, and means for preventing return of said in said one direction, biasing means for biasing said controller in said'opposite direction, means for energizing said power operated means upon demand for change in output from said stoke! mechanism, means including holding means for preventing return of the controller to its initial position while deenergizing said power operated means, and means for releasing said holding means in response to demand for further change in output of the stoker mechanism.

6. In a control system for a stoker mechanism having fuel feeding means and air feeding means, the combination of, means responsive to the demand for heat from the stoker mechanism forv controlling the operation thereof, a controller for varying the feeding of air, a first power operated means controlled upon demand for change in output of the stoker mechanism for actuating said controller toward a predetermined position,

a second power operated means for shifting said controller to said predetermined position, and

means actuated upon movement of said controller partially toward said position for causing said second power operated means to function.

'I. In a control system for a stoker mechanism having fuel feeding means and air feeding means, the combination of. means responsive to the demand for heat from the stoker mechanism, for controlling the operation thereof, a controller for varying the feeding of air, a first power operated means controlled upon demand for change in output of the stoker mechanism for actuating said controller toward a predetermined position, a second power operated means for shifting said controller to said predetermined position, and means actuated after initial movement of said controller by said first power operated means for causing operation of said second power one'rated means and for' rendering said first'powcr operated means inoperative.

8. In a control system for a stoker mechanism having a retort, fuel feeding means and air feeding means, the combination of, means responsive to the demand for heat from said stoker mechanism for placing the fuel feeding means and the air feeding means into and out of operation, an air flow controller for varying the-delivery of air from the air feeding means to the retort, a temperature responsive means for positioning said flow controller, electric heating.

means for locally heating said temperature responsive means, and means for controlling the flow controller in accordance with the air fed to the retort, said last mentioned means includinga device actuated to a substantial extent by the air passing from the'air feeding means to the retort for controlling said electric heating means.

9. In a control system for a stoker mechanism having a retort, fuel feeding means and air feeding means, the combination of, means responsive to the demand for heat from said stoker mechanism for placing the fuel feeding means and the air feeding means into and out of operation, an

aavaaes air flow controller for varying the delivery of air from the air feeding means to the retort, a temperature responsive means for positioning said flow controller, electric heating means for 10- cally heating said temperature responsive means, first control means controlled by the air passing from the air feeding means to the retort, second control means actuated in accordance with the position of the air flow controller, and means actuated by the first and second control means for controlling said electric heating means.

10. In a control system for a stoker mechanism having a retort, fuel feeding means and all feeding means, the combination of, means responsive to the demand for heat from said stoker mechanism for placing the fuel feeding means and the air feeding means into and out of operation, an air flow controller for varying the delivery of air from the air feeding means to the retort, a heat motor including a temperature responsive actuator and electric heating means for heating the same, said actuator being arranged upon heaitng thereof to move said controller in a manner to increase the delivery of air to the retort, a switch for controlling said electric heater, and means responsive to the pressure of the air delivered by said air feeding means for opening said switch upon fall in said pressure.

11. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for driving at least one of said feeding means, the combination of, means responsive to the. demand for heat from the stoker mechanism for placing said motor into and out of operation, an air flow controller for varying the delivery of air to the retort, electric power actuated means for actuating said controller, said electric power actuated means being also controlled by .said responsive means and serving to move said flow controller to increase the delivery of air when said motor is in operation, switching means for controlling said electric power actuated means, and means responsive to the static pressure of the air being delivered to' the retort for actuating said switching means in a manner to cause decrease in air delivery upon fall in said pressure.

12. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for driving at least one of said feeding means, the combination of, means responsive to the demand for heat from the stoker mechanism for placing said mo-' tor into and out of operation, an air flow controller for varying the delivery of air to the retort, electric power actuated means for actuating said controller, said electric power actuated means receiving power from th motor circuit and adapted when energized to move the flow controller to a position increasing the delivery of air and to prevent return thereof to its initial position, a switch in circuit with said power actuated means, and a device responsive to the static pressure of the air being delivered to the retort for actuating said switch.

due to the action of the air contacting it, means including a thermostatic actuator and heating means therefor for actuating said damper toward open position upon energization of the heating means, means for deenergizing said heating means when the motor is deenergized and for energizing said heating means when the motor is energized, whereby the damper is substantially closed when the motor first starts and remains closed until the thermostatic actuator becomes heated at which time the damper isopened, and means responsive to the pressure of the air delivered by the air feeding means for causing said damper to move toward closed position when the air pres sure falls below a predetermined value.

14. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for driving at least one of said feeding means, the combination of,

means responsive to the demand for heat from the stoker mechanism for placing said motor into and out of operation, an unbalanced damper for controlling the flow of air from said air feeding means to the retort, said damper tending to close at least partially due to the action of the air contacting it, means including a thermostatic actuator and heating means therefor for causing movement of said damper from substantially closed position toward open position 'upon change in temperature of the thermostatic actuator in one direction, means for controlling the heating means in accordance with operation and non-operation of the motor in a manner to cause the temperature of said thermostatic actuator to change in said one direction when the motor is started whereby the damper is substantially closed when the motor first starts and opens as the thermostatic actuator changes in temperature in said one direction, and means responsive to the pressure of the air delivered by the air feeding means for causing said damper to move toward closed position when the air pressure falls below a predetermined value.

15. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for driving at least one of said feeding means, the combination of, means responsive to the demand for heat from the stoker mechanism for placing said motor into and out of operation. an air flow controller for varying the delivery of air to the retort, control means including a pressure responsive device responsive to the pressure of the air being delivered to the retort and a thermostatic device having heating means therefor to control the position of said air fiow controller, said control means being arranged to maintain the air flow controller in substantial flow preventing position for a period of time following starting of said motor and alsoto maintain said controller in substantial flow restricting position when the air delivery pressure is below a predetermined value.

16. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for drivingat least one of said feeding means. the combination of, means responsive to the demand for heat from the stoker mechanism for placing said'motor into and out of operation, an air flow controller for varying the delivery of air to the retort, control means includ ng means responsive to the pressure of the air and a thermostatic device subject to the influence of heating means for controlling the position of said air flow controller, said control means being arranged to maintain the air flow controller in substantial fiow preventing position for a period of time following starting of said motor and also to maintain said controller in substantial flow restricting position when the air delivery pressure is below a predetermined value, and holding means controlled'by said responsive means for maintaining said air flow controller in position to permit flow of air, said holding means being released after the demand for heat from the stoker mechanism is satisfied.

17. In a control system for a stoker mechanism having a retort and a motor driven fan for supplying air to the retort, means responsive to the demand for heat from the stoker mechanism for placing said motor into and out of operation, a damper biased toward closed position'for controlling the flow of air to the retort, means for preventing opening of said damper for a period of time following starting of said motor while causing opening of the damper thereafter, said last mentioned means utilizing the air pressure produced by operation of the fan and preventing substantial opening of the damper until the air pressure builds up to a predetermined value, and

holding means connected to and controlled by I said responsive means for holding said damper in open position, said holding means-being'released after the demand for heat is satisfied for permitting said damper to move to substantially closed position.

18. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for driving at least one of said feeding means, the combination of, means responsive to the demand for'heat from the stoker mechanism for placing said motor into i and out of operation, an air flow controller for varying the delivery of air to the retort, electric power actuated means including -a slow acting thermostatic element and electric heating means therefor adapted when energized to move said controller to a posit on increasing the delivery of air and to maintain the controller in said position, and means for supplying electric power continuously to said power actuated means upon demand for bent from said stoker mechanism.

19. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for driving at least one of said feeding means, the combination of, means responsive to the demand for heat from the stoker mechanism for placing said motor into and out of operation, an air flow controller for varying the delivery of air to the retort, a heat motor including a temperature responsive actuator and electric heating means for heating the same, said actuator being arranged upon heating thereof to move said controller in a manner to increase the delivery of a r to the retort, means controlled by said responsive means for energizing said heating means upon demand for heat from said stoker mechanism, holding means adapted when energized to prevent return of said controller to its initial position, and switching means actuated'a period of, time following ener gization of the heat motor for deenergizing the same and for energizing said holding means.

20. In a control system for a stoker mechanism having a retort, fuel feeding means, a'ir feeding means, and an electric motor 'fordriving at least one of said feeding meansthe combination of,

means responsive to the demand for heat from the stoker mechanism for placing said motor into and out of operation, an air flow controller for varying the delivery of air to theretort, a heat motor-including a, temperature responsive actuator and electric heating means for heating the same, said actuator being arranged upon heating thereof to move said controller in a manner to increase the delivery of air to the retort, means controlled by said responsive means for energizing said heating means upon demand for heat from said stoker mechanism, holding means adapted when energized to prevent return of said controller to its initial position, switching means actuated a period of time following energization of the heat motor for deenergizing the same and for energizing said holding means, and means actuated upon movement of the air flow controller the combination of, means responsive to the demand for heat from the stoker mechanism for controlling the operation thereof, a controller for varying the feeding of air, a time delay mechanism including. a temperature responsive device and heating means therefor for shifting said controller, the heating means being energized upon demand for change in output of the stoker mechanism, holding means for preventing return of said controller to its initial position, cooling means for cooling the temperature responsive device, and means actuated after movement of the controller for deenergizing said heating means and initiating operation of said cooling means.

22. In a control system for fuel burning means, in combination, a controller for varying the rate of combustion in the fuel burning means, a temperature responsive device for positioning said controller, electric heating means for locally heating saiddzemperature responsive device, flow control means for controlling thefiow of cooling medium in heat exchange relationship with said temperature responsive device, and means responsive to the demand for heat from said fuel burning means for controlling said heating means and flow control means.

23. In a control system for fuel burning means, in combination, a, controller for varying the rate of combustion in the fuel burning means, a temperature responsive device for positioning said controller, electric heating means for locally heating said temperature responsive device, flow con-' trol means for controlling the flow'of cooling medium in heat exchange relationship wlthsaid temperature responsive device, means responsive to the demand for heat from said fuel burning means for energizing said heating means upon demand for additional heat for thereby actuating said controller in one direction, and means for deenergizing said heating means and actuating said flow controller tp cause cooling medium to flow in heat exchange relationship with said temperature responsive device to thereby permit movement of said controller in the opposite direction.

24. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for driving at least one of said feeding means, the combination of, means responsive to the demand for heat from the stoker mechanism for placing said motor 'into and out of operation, an air flow controller for varying the delivery of air to'the retort, electric change in temperature of said thermostatic acmotor means including a thermostatic element and electric heating means therefor for positionswitching mechanism for controlling said electric motor means, said switching mechanism having a first position causing said air flow controller to substantially prevent air flow and having a second position causing the motor means to move the air flow' controller for supplying air to the retort, and means for moving said switching mechanism from its first position to its second position a period of time following starting of the motor and for returning said switching mechanism to its first position when the motor is placed out of operation.

25. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for driving at least one of said feeding means, the combination of,

means responsive to the demand for heat from the stoker mechanism for lacing said motor into and out of operation, an air flow controller for varying the delivery of air to the retort, electric power actuated means for actuating said controller, said electric power actuated means adapted when energized to move the flow controller to a position increasing the delivery of air and to prevent return thereof to its initial position, a switch in circuit with said power actuated means, and a device responsive to the static pressure of the air being delivered to the retort for actuating said switch.

26. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for driving at least one of said feeding means, the combination of, means responsive to the demand for heat from the stoker mechanism for placing said motor into and out of operation, an unbalanced damper for controlling the flow of air from said air feeding means to the retort, said damper tending to close at least partially due to the action of the air contacting it, means including a thermostatic actuator and heating means therefor for causing movement of said damper from substantially closed position toward open position upon change in temperature of the thermostatic actuator in one direction, and means for controlling the heating means in accordance with operation and nonoperation of the motor in a manner to cause the temperature of said thermostatic actuator to change in said one direction when the motor is started whereby the damper is substantially closed when the motor first starts and opens upon tuator in said one direction.

2'7. In a control system for a stoker mechanism having a retort, fuel feeding means, air feeding means, and an electric motor for driving at least one of said feeding means, the combination of, means responsive to the demand for heat from the stoker mechanism for lacingsaid motor into and out of operation, a damper for controlling the flow of air to the retort, said damper being based toward closed position and remaining in substantially closed position irrespective of increase in pressure on the downstream side thereof. means including a thermostatic actuator and heating means therefor for causing movement of said damper from substantially closed position toward open position upon change in temperature of the thermostatic actuator in one 'direction, means for controlling the heating means in accordance with operation and non-operation of the motor in a, manner to cause the temperature of said thermostatic actuator to change in said one direction when the motor is started whereby 7 ing said air flow controller, means including 15 the damper is substantially closed when the mocontrolling the operation thereof, a controller for varying the feeding of air, a time delay mechanism actuated upon demand for change in operation of saidstoker mechanism for shifting said controller to vary the air delivery after a period of time has elapsed, holding means for preventing return of said controller to'its initial position irrespective of said time delay'mechanism, and means controlled by said heat demand responsive means for releasing said holding means.

29. In a control system for a stoker mechanism having 'a retort, fuel feeding means and air feeding means, the combination of, means responsive to the demand for heat from said stoker mechanism for placingthe fuel feeding means and the air feeding means into and out of operation, an

air flow controller for varying the delivery of air from the air feeding means to the retort, a temperature responsive means for positioning said flow controller, electric heating means for locally heating said temperature responsive means,, and

switching means controlled by the air passing from the air feeding means to the retort and by the position of the air flow controller for controlling said electric heating means, and means also controlled by said switching means to cause movement of the air flow controller toward flow increasing position in response to movement of the controller toward flow increasing position.

man w. STUART. 

